1. Field of the Invention
The invention relates generally to fuel recovery systems for internal combustion engines and more particularly to a recovery systems for the ethanol constituent of E85 fuel for use with internal combustion engines.
2. Description of the Prior Art
One of the very first sources of emissions targeted for reduction in internal combustion engines utilized in passenger cars and other motor vehicles was blow-by, i.e., air and unburned fuel that enters the crankcase and is emitted into the atmosphere by a breather vent in a valve cover.
Since the early 1960s, positive crankcase ventilation (PCV) systems have been utilized which collect and direct the unburned fuel to the carburetor or intake manifold where it is burned in the cylinders. These systems not only eliminated this source of pollution but also slightly improved fuel economy as they ensured that fuel that was previously lost by dispersal into the atmosphere was burned in the engine.
At normal engine operating temperatures, well above the volatilization temperatures of the various fractions of conventional hydrocarbon fuel, i.e., gasoline, fuel in the blow-by moves directly through the PCV system and there is no accumulation of fuel in the crankcase. However, at start-up and in low temperature operating conditions, the fuel will condense in the crankcase. As the engine warms up, this condensed fuel vaporizes and is swept through the PCV system. Because gasoline comprises many different hydrocarbon fractions that vaporize at different temperatures, this vaporization occurs gradually over a period of time.
Recently a low emission fuel manufactured from agricultural products, primarily corn, and designated E85 has become available for consumer use in passenger cars. The fuel is nominally 85% ethanol or grain alcohol. When an E85 fueled vehicle is started or operated in a low temperature environment, some of the ethanol enters the crankcase in liquid form and mixes with the engine lubricating oil. As the engine warms up and reaches 78 degrees Celsius (172.4 degrees Fahrenheit) all of the ethanol in the crankcase vaporizes and flows through the PCV system at a very high rate. Even though the oxygen sensor has shut off fuel flow to the cylinders, in extreme cases there may be so much vaporized ethanol flowing through the PCV system that the engine runs rich and exhaust emissions are increased. At the very least, this high momentary flow of vaporized ethanol through the PCV system and engine is difficult for the engine control system to compensate for. Additionally, this event may result in drivability issues.
From the foregoing, it is apparent that improvements in fuel systems for vehicles utilizing E85 as fuel are desirable.